Connectors of this type include a metal terminal inserted into the cavity of the connector housing. An engagement mechanism, such as a lance formed by cutting and bending a section of the terminal, engages the housing and prevents unwanted withdrawal of the terminal from the housing. In addition, a retainer is mounted on the housing at an engagement position which additionally blocks removal of the terminal from the housing.
When servicing such connectors (e.g. replacing the terminals), the old terminal must be removed from the cavity. If the terminal is doubly engaged, the retainer must first be moved out of its engagement position into a release position; this will disable the secondary blocking means. After this has been accomplished, the engagement mechanism (lance) must be released.
While the retainer can be easily moved out of the engagement position, because the lance or other engagement mechanism is positioned inside the cavity, it is not easy to release. The user must insert a specially made long thin tool into the front of the cavity and probe around in order to contact the lance. Once contact is made, the lance can be pressed out of abutment with the housing and the terminal removed.
On the other hand, if a tool opening, to allow access to the lance, is formed in the housing, it would allow debris to enter and adhere to the terminals. This would impair the electrical conductivity and compromise the integrity of the connector.